Abstract

The first theoretical investigation on Cs₂CO₃-mediated [4+2] annulation of α, α-dicyanoalkene and ynone was provided by our DFT calculation. Via Cs₂CO₃-mediated deprotonation, the α, α-dicyanoalkene is initially converted into vinylogous carbanion from methyl group. Then 4-membered ring carbanion stabilized by two electron-withdrawing cyano groups is generated through nucleophilic attack of methylene on ynone followed by an intramolecular nucleophilic addition. Next the ring opening occurs from strained 4-membered ring. Subsequently the 6-membered ring closure is accomplished via a second intramolecular nucleophilic attack of methylene carbanion to cyano group determined to be rate-limiting for the whole process. Finally, the desired product m-terphenyl is obtained through aromatization of the central ring and afterwards protonation together with recovered Cs₂CO₃.

Keywords:[4+2] annulation; Intramolecular rearrangement; M-terphenyl; Aromatization; Ring opening